Mermaid Swim Fin - NEW! Improved strap and backpack included The Atlantis Fin instantly transforms any swimmer into a real mermaid. Made with a new and improved foot strap! Designed with an adjustable, quick-release strap. For safety reasons, if the swimmer starts doing a scissor kick (walking motion) in the water, the fin will come off. The adjustable strap allows for a wide range of sizes, please check the size chart before purchasing. Ideal for swimmers ages 6 and up. Comes with a reusable mesh backpack that is perfect for the beach or pool. Teaches a balanced dolphin kick and builds leg strength. Keep legs glued together like a mermaid to keep the fin on.